Cabling LAN - Part II

Crossover Cables & straight Through Cables

Ethernet cables can be wired in three different ways. The two main ways are straight through and Cross over. The third type is called as Rolled. Straight through cables are generally used to connect different types of equipment; for example, a computer  and a hub. Crossover cables are generally used to connect similar types of equipment like a computer to another computer. Inside the UTP cable there are 8 physical wires. The 8 wires are arranged in pairs: one pair is used to send information and other pair is used to receive information. For computers to communicate, the sending pair of one computer has to be connected to receiving pair of another computer. So crossover cables are required.

T568B Termination T568A Termination

RJ45 Jack

Straight-through Cable

The straight- through cable is used to connect:

• Host to switch or hub
• Router to switch or hub

Straight through Cable

Straight Through Cable

In the above figure you can see only 1,2,3 and 6 pins are used. Connect pin 1 to pin 1,2 to 2,3 to 3 and 6 to 6. Remember this would be an Ethernet cable and it will not work with voice, Token Ring, and ISDN.

Crossover cable

The Crossover cable be used to connect:

• Switch to switch
• Hub to hub
• Host to host
• Hub to switch
• Router direct to host

Same four wires are used in the cable as in the straight-through cable but different pins are connected together. In the  following figure, can see how four wires are used in crossover Ethernet cable. And notice that instead of connecting 1to1, 2to2 etc, pins 1 is connected 3, pin 2 is connected to 6 on each side of the cable.

Crossover cable pinouts

Two pairs crossed, two pairs uncrossed

Certain equipment or installations, including those in which phone and/or power are mixed with data in the same cable, may require that the "non-data" pairs 1 and 4 (pins 4, 5, 7 and 8) remain un-crossed.

T568A  - All Four Pairs Crossed

T568B  - All Four Pairs Crossed

Rolled cable

Roll Over or Console Cable

Rolled cables are not used to connect any Ethernet connections together, but rolled Ethernet cable can be used to connect a host to a router console serial communication port. Rolled cable is also used to connect PC running Hyper- Terminal to the Cisco hardware. Eight wires are used in rolled cable to connect serial devices, although not all eight are  used to send information just as in Ethernet networking. Figure below shows eight cables used in a rolled cable.